ML18283B711

WM28-1-67-100 Analysis of Flow Patterns in the Vicinity of Browns Ferry Nuclear Plant Intake.

ML18283B711
Person / Time
Site:	Browns Ferry
Issue date:	01/31/1978
From:	Herren H, Waldrop W Tennessee Valley Authority
To:	Office of Nuclear Reactor Regulation
References
WM28-1-67-100
Download: ML18283B711 (65)

Text

. Tennessee Valley Authority Division of Water Management Water Systems Development Branch ANALYSIS OF FLOW PATTERNS IN THE VICINITY OF BROWNS FERRY NUCLEAR PLANT INTAKE Report No. WM28-1-67-100 By William R. Waldrop and Herman L. Herren Norris, Tennessee 7anuary 1978

1 INTRODUCTION TVA's Browns Ferry Nuclear Plant (BFNP), situated on Wheeler Reservoir of the Tennessee River in north Alabama (Figure 1), has a design capacity of 3456 MW with three generating units. The pl.>nt. was originally designed to operate in Open Mode for condenser cooling. In this mode, water is pumped from the river through the steam condenser the cooling water is heated l'here before being discharged through submerged multiport diffusers in the river.

The plant has been retrofitted with six mechanical draft. cooling towers, two per unit, to provide the plant operators with the option of cooling the condenser cooling water.

The possible environmental conseqences of thermal discharges are well documented, but the water temperatures at which these effects are discernable are not well defined. Thermal water quality st,indards were promulgated generally to limit the maximum temperature and lem-perature rise of the adjacent water body.

The environmental effects of plant intakes are also of concern.

Fish may be trapped within intake structures or canals and become impinged against the intake screens. Fish and other aquatic organisms too small to be impinged on the intake structures may be entrained in the cooling system of the plant. The rate of impingement and entrain-ment of aquatic organisms is influenced by many factors such as the condenser flow rate, configuration of the intake structure and source of water.

This report presents results of a hydrodynamic field investiga-tion of the flow in Wheeler Reservoir in the immediate vicinity of the

H

/

TENN E.SSEE ALABAMA WHEELER DAM TRM 275 BROWNS FERRY 280::.. + 0 NUCLEAR PLA NT TRM 294 HUNTSVILLE 300 3IO DECATUR Q

"'~ 'ii'b5'~>. i" "':"' 'i'".  !~

FLOW ",, "'::. 4,0 TENNESSEE RIVER SCALE 20mi G UNTERSV I LLE IO DAM TRM 349 IO 20 30 km Figure l: Location Map of Browns Ferry Nuclear Plant

3 intake structure of BFNP. The tests were planned to achieve two objectives:

~

1. To provide'upporting hydrodynamic data for a biological evaluation of the environmental effects of the condenser cooling water intake system at BFNP.

2. To verify results of a computer model being developed by the'niversity of Tennessee under the auspices of the Division of Wildlife and Fisheries of the Depar tment. of Interior.

Results and analyses of the field tests conducted for several reservoir flow and plant operational conditions are included.

PHYSICAL CHARACTERISTICS This section describes the general features of the reservoir and the plant which affect the flow patterns in the vicinity of the plant intake structure.

'I'he Site The BFNP is situated on the right bank of Wheeler Reservoir at Tennessee River Mile (TRM) 294. River flows in the vicinity of the plant are primarily dependent upon discharges from Guntersville Dam (TRM 349), which is 55 miles (88 km) upstream, and from Wheeler Dam (TRM 275), which is 19 miles (31 km) downstream. The mean annual flow rate of the river at BFNP is 45,000 ft3 /sec (1270 m 3

/sec). Since discharges from these dams are normally used for hydroelectric genera-tion at periods of peak power demand, the flow in Wheeler Reservoir is often unsteady. As a result, flows near the plant usually change drastically throughout the day.

Under present operating practices, the water level in Wheeler Reservoir varies no more than six feet (1.8 m) throughout the year.

From approximately April through 3uly, the reservoir elevation fluctu-ates only slightly from the maximum level while during most of the remainder of the year the surface elevation is five to six feet (1.5 to 2.0 meters) below the maximum.

The 14-mile (23 km) reach upstream of the'plant is character-ized by a main river channel, which was the original riverbed, flanked by wide, shallow overbank regions (Figure 2). The main channel is approximately 30 feet {9 m) deep and 2000 feet {600 m) wide. The right overbank region immediately upstream of the plant is relatively

Figure 2: Location of Temperatue Monitors shallow with the exception of an old creek channel adjacent Lo the right.

bank which is approximately 20 feet (6 m) .deep. However, when the II reservoir elevations are near maximum, depths in most of the right overbank region, upstream of the plant range from five to ten feet (1.5 to 3 m). During low reservoir elevations, the overbank is exposed in some regions and is approximately three feet (one m) deep in others.

The proportion of flow between the main channel and the over-bank depends upon the reservoir elevation and the total flow in the reservoir. A significantly greater percentage of the total flow is con-fined to the main channel during the months when the reservoir eleva-tions are low. For both high and low reservoir elevation, during h

higher flows a higher percentage can be expected in the main channel because the effect of bottom friction is more pronounced in the over-bank than in the main channel. Under all conditions, the majority of the river flow is confined to the main river channel in this region.

The Plant Condenser cooling water for BFNP is pumped from an inl >ke basin which is separated from the Wheeler Reservoir (Figure .'l) by a shallow skimmer wall extending approximately 10 feet (3 m) below the normal maximum surface elevation. A dredged channel approximately 35 feet (10 m) deep extends from the intake basin to the deepest part of the main river channel as shown in the underwater topography of Figure 3. This dredged channel permits flow from the lower depths of the main channel to enter the intake basin as well as the flow from the right overbank region of the reservoir.

INTAKE PUMPS FOR UNITS INTAKE CHANNEL ANIIEL CIIAN URN r

I I " '550""'""

SKIMMER WALL

~~ ~<0 540 K% OII 0>

TDNCSIKE RIVKII WHEELER RESKRVOIR Sgq NOTE:

MAX POOL EL 555 MIN POOL EL 550 ~ SCALE N

50 100m

~

Figure 3: Underwater Topography Near the BFNP intake

C'I The plant condenser cooling water system can be ope> ated in three modes: Open, Helper and Closed. In the Open Mode, I,he con-denser cooling water is discharged directly into the river I,hrough submerged multiport diffusers. When this method of disposing of the excess heat from the plant is not sufficient to meet applicable thermal standards, the condenser'ooling water may be routed to the cooling towers and the effluent from the cooling towers routed to the diffusers for discharge into the river (Helper Mode), or routed to the plant intake channel for reuse as condenser cooling water (Closed Mode).

These three modes of operation of the BFNP cooling system are illus-trated in Figure 4.

3 In the Open Mode, the plant pumps 4410 ft3 /sec (125 m /sec) 3 from the river of which 4350 ft3 /sec (123 m /sec) are pumped through the steam condenser. As the cooling water passes through the con-denser, it is heated approximately 25'F (14'C) before being discharged through submerged, multiport diffusers into the river. When operating in the Helper Mode, the plant intake flow rate is 3675 ft3 /sec (104 m /sec) with a slightly higher design condenser rise of 31. 7'-F (17.6'C). In the Closed Mode of operation, only a small quantity of 3

water, between 200 and 300 ft3 /sec (5.7 and 8.5 m /sec), is drawn from the river primarily for "makeup" water for the cooling system.

Although there are fewer potential environmental effects from the Closed Mode of operation, the power required to operate the cooling tower lift pumps and fans, and the loss of generating efficiency which results from increased cooling water temperatures can produce a.net loss in generation of as much as 150 MW at the BFNP.

COOLING.

TOWERS HELPER CLOSED POWERHOUSE Tl NTAKE THOT OPEN TCOLD HELPER

':::::;. 'NTAKE

":": CHANNEL CLOSED 2 LLI TRIVER TMIXED D IFFUSERS

~RIVER Figure 4: Schematic of Three Condenser Cooling Modes of Browns Ferry Nuclear Plant

10 FIELD INVESTIGATIONS Three procedures. were used to analyze the flow field in the vicinity of the BFNP water intake. Velocities were recorded from a boat anchored at several locations both inside and outside of the intake basin. These measurements produced velocity vectors in the horizontal plane. Drogues released at various locations ari'd designed to move with the horizontal flow at a specified depth were also tracked. The trajec-tories 'of these drogues provided an indication of pathlines of the flow entering the intake basin. In addition, the flow in the right overbank region upstream of the plant intake was traced with a flourescent dye.

The concentration of dye in the overbank area immediately upstream of the plant intake was recorded and compared to the maximum recorded concentrations of dye inside the intake basin. The dilution of the concentration of dye inside of the intake gate was attributed to water being withdrawn from the main channel which contained no dye. Al-though these three procedures were sometimes used concurrently, I.hey will be discussed separately.

Water temperatures of the survey area'ere obtained from two permanent water temperature monitors at TRM 295.8 (Figure 2). Each of these monitors has 'a string of several ther'mistors positioned at prescribed depths and recorded the water temperature hourly. Monitor 7 indicates water temperatures of the overbank area and Monitor 14 provides temperatures of the main channel. Both are considered accu-rate to +0.2'F (0.1'C).

V~li 8 Procedure and Conditions On,May 17 and 18, 1977, velocities were recorded in the int.ake I basin and in the reservoir near the intake. Measurements were made at depth increments of 3.3 feet (1;0 m) from an anchored boat using a Marsh-McBirney electromagnetic current meter. This instrument utilizes the electric field generated by water moving through a magnetic field to determine two components of the velocity vector over a range ol zero lo three meters per second with an accuracy of +0.05 ft/sec (1.5 cm/sec).

During this survey, all of the condenser cooling water pumps were in operation producing a total intake flow rate of 4410 ft /sec (125 m /sec). The plant was operating in the Open Mode throughout these tests. The Tennessee River flow rate was computed to be 38,000 ft /sec (1075 m /sec) with a water surface elevation of approximately 555.6 ft (169.0 m).

Water temperatures in the overbank were 1 to 2'F (0.5 to 1.0'C) warmer than those at comparable depths. in the main channel.

Results Velocities measured at the surface and at depths of 3.3, 10, 16 and 23 feet (1.0, 3.0, 5.0 and 7.0 m) in the main channel and, where depths permitted, in the overbank areas upstream of the intake are presented in Figures 5 through 9, respectively. Winds were relatively calm during the survey period; therefore, surface velocities were un-disturbed. These data reveal that velocities in the vicinity of the old creek channel near the right bank of the overbank region were slightly greater than in the more shallow regions of the overbank, but even

1 l2 INTAKE PUMPS FOR UNITS IN Tj4 KE RECUR CHANNEL ":I CH<NN SKI MMER WALL OVERBANK TE NNESSEE R IVER WHEELER RESERVOIR VECTOR SCALE MAP SCALE 50 cm/sec 0 500 fi 2 ft/sec 0 50 IOO '150 m FIgure 5: Velocity hleasurements at Water Surface for Browne Ferry Nuclaor Plant on May l8, l977

INTAKE PUMPS FOR UNITS INTAKE RECUR CHANNEL CHANNEL SKIMMER WALL OVERBANK 4 ~

~

~

~

TENNESSEE RIVER WHEELER RESERVOIR VECTOR SCALE MAP SCA LE 50 cm/sec 0 500 ft 0 2 ft/sec 0 50 100 I 50 m Figure 6: Velocity Measurements at I Meters Depth for Browns Ferry Nuclear Plant on May l8,1977

I NTA KE P UMPS FOR UNITS INTAKE REru RN CHANNEL CggNNE S KIMMER WALL OVERBANK TENNESSEE RIVER WHEELER RESERVOIR VECTOR SCALE MAP SCALE 50 cm/sec 500 ft 2 ft/sec 0 50 IOO l50 'm Figure 7: Yelocity Measurements at 5 Meters Depth for Brogans Ferry Nuclear Plant on May I8, l977

I5 INTAKE PUMPS FOR UNITS INTAKE RE'TU CHANNEL ":.

RN CONN E'g SK IMMER WALL kd ~

OV B K TENNESSEE RIVER WHEELER RESERVOIR VECTOR SCALE MAP SCALE 50 cm/sec 500 ft 2 ft/sec. 0 50 IOO I50 Al FIgure 8; VelocIty Measurements at 5 Neters Depth for Browne Ferry Nuclear Plant on May IS, l977

l6 INTAKE PUMPS FOR UNITS INTAKE RETVRN CHANNEL CHAIIlgEL S KIMMER WALL OVERBANK TENNESSEE RIVER WHEELER RESERVOIR VECTOR SCALE MAP SCALE 0 50 cm/sec 0 500 ff 2 ft/sec 0 50 IOO l50 m Figure 9: Velocity Measurements at 7 Meters Depth for Browns Ferry Nuclear Plant on May l 8, l 977

l7 those velocities near the right bank were somewhat less than those of the main channel. A numerical integration of the velocities revealed that the total flow of the overbank was approximately 3000 ft3 /sec (85 m /sec) during this river flow and stage.

Velocities near the surface (Figure 5) in the immediate vicinity

'f the intake show 'a downstream component implying that some of the surface flow from the overbank area was not entrained into th>> plant.

This is attributed to buoyancy produced by the warm surface temper-atures ol'he overbank water. This condil ion is LypIcal dui ing I.h>>

spring because the large surface area of the shallow, slower flowing overbank regions have less thermal inertia than the main channel and hence warm more rapidly.

At depths of 10 feet (3 meters) or greater, the velocity vectors indicate that all flow in the dredged intake channel to the plant were directed toward the plant. This water appears to have come primarily from the main channel of the reservoir. Water flowing at depths of less than 10 feet (3 meters) in the reservoir near the plant intake came primarily from the overbank.

Velocities recorded inside the intake channel are presented in Figure 10. The location of this cross-sectional view of the channel is denoted in Figure 9. These data indicate that the flow in the intake channel is evenly distributed both top to bottom and side to,side. The mean velocity at this cross-section is 1.3 ft/sec (39 cm/sec).

Is WS EL.555;6 ff m 0 0, 43 34 3T 40 IO 48 4l I()

48 40 III l5 z: 5m 27 40 I-LLJ II)

O /y 27 27 20 lg)

II'5 40 VELOCITY, cm/sec 30 ft lj

/~ghj 10m lt ty 20 60 80m 50 IOO I50 200 250 0 DISTANCE FROM LEFT SIOE OF INTAKE CHANNEL SECTION A-A Figure IO '. Velocity Measurements 75 Meters from the Intake Pumps, May 17, I977

19 D~ro ue Trajectory Analysis.

Procedure and Conditions On July 20 and 21, 1977, flow patterns in the reservoir near the intake were investigated with drogues. These drogues had broad lateral fins one foot (0.3 meters) high (Figure 11). These fins created high drag at the depth of the fins and thereby moved with the hori-zontal flow at that depth. A float and weight kept the drogue vertical r

and the fins at the prescribed depth. The floats were color-coded and were tracked visually with surveying transits positioned at two locations on the shore.

Intake flows varied between 3400 ft3 /sec 3

{96 m /sec) and 4000 ft /sec (113 m /sec) during the surveys. River flows fluctuated be-3 3 tween 20,000 ft /sec, (566 m /sec) and 25,000 ft3 /sec (710,m /sec) on July 20, and remained relatively constant near 36,000 ft3 /sec (1020 m /sec) on July 21 ~

Winds were variable during both days but generally increased in intensity throughout the day. During some of the tests, the wind obviously affected the drogues nearest the surface, i.e., 1.5-fooL (0.5-meter) depth. Those cases are noted on the data to be present.ed.

Because the reservoir had entered the cooling phase of its annual cycle, water temperatures in the overbank were typically 1, to 2'F (0.5 to 1.0'C) cooler, than those at comparable depths in the main channel.

Results The results of the drogue analysis for the tests conducted on July 20 are, presented in Figures 12-14; and for the tests conducted on July 21 in Figures 15-17. Trajectories for fins.positioned at depths

FLOAT WATER LINE

~FINS WEIGHT Figure II: Drogue used for Trajectory Analysis

INTAKE FLOW- 5600 fts/aec (l02 ms/aec)

INTAKE PUMPS UNITS r FOR I

INTAKE CHANNEL C~~

BEquII" SKIMMER. WALL WIND EFFKCTKD LEOEND:

oi l.b fl (0.46m) DEPTH a.b fl (I.5m)DEPTH

~ ~ 20ft (6.I m ) OEPTH OVERBANK T ENNESS EE R I VK R WHEELER RESERVOIR RIVER FLOW-25,000 fts/aec (708 ms/aec)

SCALE NOTE:

TRAVEL TIMK BETWEEN 400 fl SYMBOLS IS E40 SKCONDS 0 50 lOOm Figure l 2: Drogue Tr'ajectories From 0700 hrs 'o 0830 hrs on J uly 20, 1977

IV 22 INTAKE PUMPS INTAKE FLOW 3900 fts/sec (I IO ms/sec)

FOR UNITS INTAKE CHANNEL SKIMMER WALL WIND EFFECTED LEGEND:

(y~ I.5 tt (Oe46m) DEPTH 5 ft (6.lm) DEPTH l b ~

l NOTE:

TRAVEL TIME BETWEEN SYMBOLS IS 240 SECONDS OVERBANK 6,

4 TENNESSEE RIVER WHEELER RESERVOIR RIVER FLOW l9,600 ft /sec (555 m /sec)

SCALE 0 200 400 II 0 50 100 m Figure I3: Drogue Trajectories From 0900 hrs To l030 hrs on July 20, i977

INTAKE PUMPS INTAKE FlOW 5450 ft /SBC (98m /sec) r FOR UNITS INTAKE CHANNEL CSA~"'"

SKIMMER WALL

~WIND EFFECTED LEGEND:

o ~ I.d tt (0.46m) DEPTH 4, ~ 5 tt ( I.S m) OE P TH

~ . 20rt (6.I m) OEPTH NOTE:

TRAVEL TIME BETWEEN SYMBOLS IS 240 SECONDS DROGUE DRAGGED BOTTOM l OVERBANK WIND EFFECTS BECAME DOMINATE TENNESSEE RIVER WHEELER RESERVOIR RIVER FLOW 20,500 fts/Sec (58I m. /sec)

SCALE 0 200 400 tt 0 50 IOO m Figure 14: Drogue Trajectories From 1045 hrs To 1245 hrs on July 20, 1977

INTAKE PUMPS FOR UNITS INTAKE FLOW-5450-ft /eec (98m /eec)

'I INTAKE CHANNEL tt C REqu+

SKIMMER WALL LEOENO:

e I.S ft (0.46 m ) DEPTH Ric tt ( l.5m)DEPTH

~ ~ 20tt (6.I m) DEPTH

)

NOTE:

TRAVEL TIME BETWEEN SYMBOLS IS 240 SECONDS TENNESSEE RIVER I L OVERBANK WHEELER RESERVOIR RIVER FLOW -56,500 ftS/eec (l055 ttts/eec)

SCALE 200 400 ft a 0 SO 'oom Figure l5: Drogue Trajectories From 0830 hrs To l000hrs on July 2I, l977

25 INTAKE PUMPS FOR UNITS INTAKE FI.OW -3900 tt /eec (IIO m /sec)

INTAKE4 ICHANNEL Ic BE<uS" SKIMMER WALL LEGEND:

8 I.B ft (0.46 m ) DEPTH 4~ S ft ( l.5 m ) DE PT H

~ ~ 20 ft (6.lm) DEPTH NOTE:

TRAVEL TIME BETWEEN SYMBOLS IS 240 SECONDS OVERBANK 0,

~

p

~~

~

~

0, TENNESSEE RIVER WHEELER RESERVOIR

"., RIVER FLOW 35,200 tt /eec (997 m /eec)

'O.

~

~~

o~

p

~ ~

8., ~ ~

~

40 tg

~y

~~

08 ~y

~ ~ ~

~~

SCALE 0 ~~

~ ~ ~

8oo ~~

0 200 400 ft

~

8 50 lOOm

'8

~

~

Figure 16: Drogue Trajectories From 1050 hrs To ll30 hrs on July 21, 1977

26 INTAKE PUMPS FOR UNITS INTAKE FLOW-3900 tts/soc (IIO ms/soc)

INTAKE CHANNEL C~

BEt~q~

SKIMMER WALL LEOENo:

e ~ l.e tt (0.46m) DEPTH e.S tt(I.5m)DEPTH o ~ SO tI (6. I m) DEPTH OVERBANK NOTE:

TRAVEL TIME BETWEEN SYMBOLS IS R40 SECONDS TENNESSEE RIVER WHEELER RESERVOIR RIVER FLOW- 36,300 ft /sec(l028 m /soc)

SCALE 0 200 400 fl 0 50 IOO Ill Figure l7.'rogue Trajectories From l400 hrs To l500 hrs on July 2l, l977

27 I

of 3.5 I'eel. (0.5 m), 5.0 I'eet (1.5 m), and 20 I'eet (6 m) an sly<>wn.

Symbols showing drogue positions at'ntervals of 240 seconds provid>> an indication of 'he speed at which each drogue was moving along its trajectory.

On July 20, when the river flows were relatively low, all drogues released on the overbank drifted to the upstream side of the intake. One drogue released in the main channel approximately 300 feet (100 m) from the right overbank tracking flow at a depth of 20 feet (6 m) (Figure 14) drifted into the dredged channel and ultimately against the downstream side of the intake gate implying that water from the lower depths of the right side of the main channel was fiowing into the intake channel. Another drogue released near the center of the main channel (Figure 12) appeared relatively unaffected by the intake flow.

Trajectories were considerably different on July 21 when flows

'I were much higher. The downstream inertia of the river flow appeared to have had a more pronounced effect upon the flow patterns near the intake. As a result, the overbank flow nearest the right bank ap-peared to.enter the intake on the upstream side; f]ow from the center of the overbank entered the middle; and flow from the ouler edge and the channel entered on the downstream side of the intake. Although not verified by these drogue studies, results of the previous velocity F

survey (May I

18) conducted under similar flow conditions indicated that water from the lower depths (i.e., below the 20 feet [6 m] drogue) of the right side of the main channel also flowed into the plant intake channel. This is also implied from the results of the dye studies to be presented subsequently.

28

, D e Studies t

Procedure and Conditions A portion of the overbank upstream of the plant intake was injected with a fluorescent dye in order to determine the fraction of water in the plant intake channel obtained from the overbank. Dye concentrations recorded immediately upstream of the intake gate were t

compared with concentrations recorded inside of the intake channel.

4 The lower concentrations in the intake channel provided a quantative measure of the dilution attributable to the influx of water from the main channel which contained no dye.

The dye was injected approximately 0.6 miles (1 km} upstream of the intake. A zone'approximately 1000 feet (300 m) long extending across the entire breadth of the right overbank was injected with a 20 percent solution of Rhodamine WT dye, a very dark red, aqueous liquid which is particularly suitable for flow tracing by fiuorometry and visual methods.

The dye was injected into the water through two 1.5-inch (3.A 1

cm) diameter manifolds'rigidly mounted on each side of a boat (ligure 18). Dye was supplied from a 30-gallon (115-liter) drum which was kept under constant pressure to assure an even flow of dye. Dis-charge ports in the manifold were positioned at depths of 0.5, 2.5, and 5.0 feet (0.15, 0.76 and 1.5 m). By throttling the boat to selected speeds and varying the flow from the discharge ports, the desired con-centrations could be achieved. Turbulence of the boat wake and natu-ral dispersion as the water flowed toward the plant provided vertical and horizontal mixing and thus minimized dye concentration gradients in the overbank near the plant intake.

Boats equipped with Turner Model 111 or Model 10 fluorometers and anchored at predetermined monitoring stations were used to obtain

29 1

I

.~y-c

'R Figure 18: Dye Injection Procedure

30 samples of the water 'at various depths. These data were used to determine maximum concentrations of dye at various locations as the dye cloud passed from the overbank and through the intake channel.

8 Four separate surveys were conducted for river flows ranging 3

from 11,000. ft3 /sec (310 m /sec) to 38,000 ft3 /sec (1075 m 3

/sec).

These flows were obtained through prearranged special operation of the upstream and downstream hydroelectric plants. The plant was operat-ing in Open Mode during the survey on May 18, and was operating in a combination of Open and Helper Modes for the latter three tests.

During the spring survey (May 18), the water temperature in the overbank was significantly warmer than the main channel, but by July 20 when the last test was conducted, this condition had 'eversed.

Specific plant operating conditions and ambient conditions existing during each test are provided with the discussion of that test.

Results Although the four tests were conducted for a wide range of plant operational and river conditions, the percentage of water pumped into the plant from the overbank is remarkably consistent. Each 'test will be discussed separately.

mum value M~f8 of 4410 1977 fh ft /sec 1

7 (125 m 9 fl

/sec).

f kh 11 <<h River flows were constant at 38,000 ft /sec (1075 m /sec), and the temperature in the overbank was detectably warmer than in the main channel (Figure 19) and the over-bank existed near the latter part of the survey period and thereafter.

Because of the buoyancy of the flow from the overbank when it merged with the cooler water from the main channel near the plant

51 SURVEY 50 PER IOD 12 40 O Vl IO g

'rn~

8

~O0 COMPUTED FLOW 0 20 TENN. RIVER MILE 293.5 0 0,0 LLJ 4

.10 0 'I 0

TIME, hrs 90 Ij MONITOR N0,7, 30 0

(OVERBANK) o 0

ILI 28 ~

I- 80 D 2.5ft (,76m) DEPTH 26 ~+

ILI r v K Q. 24 ILI LLJ 15 ft (4,6%) DEPTH X I- 22 LLJ I-70 TIME, hrs 90 IL MONITOR NO. I4 0 30 (CHANNEL) 0 ILI 28 LLj

]~

~I- 80 2.5 ft (.76m) DEPTH~ 26 K

ILI 0

gl l7 ft(5.2m) DEPTH 24 Pu ILI I- 22 ILI I-70 0600 ,I 200 I 800 2400 TIME, hrs Figure19'. River Flow and Temperature vs Time May I8, l977

32 intake, a portion of t.he water from t.h>> upper three feet; (one meler) ol'he water column was not entrained into the plant intake. A qualilaliv>>

description of the warm surface affected at any time (not simultane-ously) by the re'd dye is shown in Figure 20, which indicates that the dye was .visible until it was thoroughly mixed with the discharge from the diffuser.

Quantative sampling on the overbank immediately upstream of the intake revealed average dye concentrations of 20 parts per billion (ppb) by volume. Comparing this to the maximum value, 11 ppb of the

'cross-sectional average of concentrations recorded in the intake channel midway between the skimmer wall and the pumps, indicated that ap-proximately 55 percent of the flow entering the plant came from the overbank. These test conditions and results are summarized in Table 1 I

along with data from the remaining three tests.

3une 7, 1977--During the second test, river flows of 35,000 ft /sec (1000 m /sec) were similar to those of May 18. However, the thermal structure of the reservoir was slightly different and the plant was operating with lower intake flow rates as shown in Figures 21-22 and summarized in Table 1; The downstream inertia of the overbank flow and the slight temperature difference produced a qualitat.ive pic-ture of the surface, presented in Figure 23, which is similar to Figure 20 (May 18 test).

The sampling positions for measuring dye concentrations are also denoted in Figure 23. 'oncentrations recorded in the reservoir and in the intake channel are presented in Figures 24 and 25, respec-tively. Because of the proximity to the dredged channel leading to the plant intake, it was determined that data recorded at Station A

//

/

//

//

//

// /

Pgpl g/

INTAKE PUMPS FOR UNITS 0@ +~ Z'5 Cr

+~+~ / ~

OVERBANK MILE

+ SEEDING ZONE 294 DYE MONITORING STATION DIFFUSER TENNESSEE RIVER MASON ISLAND LIGHT 294.9 WHEELER RESERVOIR SCALE 0 500 IOOO ft MILE+ 295 0 I 00 200 300 ITI Figure 20:Seeding Zone, Monitoring Stations And Observed Behavior of Dye Cloud May l8, l977

50 SURVEY l4 PER IOD l2 40 O IO u 30 8 ro~

~O W 0 0 00 20 COMPUTED FLOW)

TENN. RIVER MILE 293.5 0

4 IO

-2 0

90 MONITOR N0.7 (OVERBANK) 30 o 0

W 28 WK 2.5 ft (.76m) DEPTH~

~ 80 26 ~~

l5 ft { 4.6 m ) DEPTH 24 ~W 22W 70 90 U

0 I4 MONITOR NO. 30 W (CHANNEL) 0 I- I5 ft (4.6%) DEPTH 28 W

+ 80 W

26 ~

CL LLI 2.5 ft {o76%) DEPTH 24 W I-22 W 70 I-0 0600 I 200 1800 2400 TIME, hrs Figure 21: River Flow and Temperature vs Time June 7, 1977

SURVEY PER IOO l2 IO I- 30 UNIT 5 O CO 4J O 20

,6n

~~ o I- UNIT 2 R

Q.

R IO UNIT I 0600 1200 1800 2400 TIME, hrs Figure 22: Condenser Cooling Water Flow For June 7, l977

INTAKE PUMPS FOR UNITS a

OVERBANK r

MILE SEEDING ZONE DYE MONITORING 294 STATION TENNESSEE RIVER DIFFUSER WHEELER RESERVOlR MASON ISLAND LIGHT 294.9 SCALE 0 500 IOOO ft MILE+ 295 0 IOO 200 300%

Figure 25:Seeding Zone, Monitoring Stations And Observed Behavior of Dye Cloud June 7, l977

LEGEND:

8 = 2 ft (0.6 m ) DEPTH

6) El =6 ft ( I.Bm) DEPTH 0 = l2 fl(3.7m) DEPTH tL O

I- 20 K

I-LLj

/ ~

O / ~

~

~

~

Z ~

~ ~

O lp I,'4 LLJ

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0 TIME, hrs STATION A Q3 CL Q.

O I- 20 0

I-R ILJ O

R 0

O lp UJ O

0 e 0900 IOOO I lpp I 200 TIME, hrs STATION B Figure 24: Dye Concentration Outside of Skimrner Sall June 7, t977

Q 20 f

Q ~ LEGEND:

0 = 2 ft (0.6m) DEPTH O 8 =10 ft (3. I m ) DEPTH Lh =20 ft(6.1m) DEPTH IO LLI R

Q O

UJ Cl 0 TIME, hrs STATION D Q. 20 Q.

R O

I-Q I- IO LU C3 R

O O

td TIME, hrs STATION E rD 20 O

I-IO hl O

O O

0 09 00 1000 1100 1200 TIME, hrs STATION F Figure 25: Dye Concentration in intake. Channel June 7, l977

39 reflected some mixing with flow from the main channel..Hence, Station B was used to determine a depth-averaged peak overbank dye concen-

'tration of 22 ppb. Comparing 'this concentration with the maximum concentration determined by averaging across the cross-section of the intake channel, 13.8 ppb, it was determined that approximately 63 percent of the intake f)ow came from the overbank; June 19 1977 River flows were significantly lower than during any of the other three tests, averaging about 11,000 ft3 /sec (310 m /sec). There was no appreciable difference in water temperatures in the region surveyed (Figure 26) and the intake flow was constant at 3420 ft.'/sec (97 m /sec) (Figure 27). For these conditions, Ih>> (lunli-tative picture of the surface (Figure 28) reveals I

a different flow pat-tern as all of the overbank flow seemed to be drawn into the intake.

Data from the reservoir monitoring stations (Figure 29) were used to estimate an average o>erbank dye concentration of 23 ppb.

Dye concentrations recorded in the intake channel (Figure 30) show that during these low river flows, flow from the overbank was confined to the right side of the intake channel with water from the main river channel on the left side. These data produced a maximum cross-sectional average concentration of 12.7 ppb, which indicated that 55 percent of the intake flow came from the overbank (Table 1).

7~123. 1977 3 3 3 1 11 7719 317 9 3 1 9 flow (Figure 32) were somewhat unsteady, averaging 21,000 ft3 /sec (596 3

m /sec) and 35,500 ft /sec (1005 m /sec), respectively. Because the reservoir had begun its annual was in a cooling phase, the overbank temperatures were slightly cooler than those of the main channel (Figure 31 and Table 1). Where the two water masses met, the main

40 50 14 l2 40 SURVEY O og

~" PERIOD IO g IL. 30 8

~O0 COMPUTED FLOW, TENN RIVER MILE 293.5 00 0,0 20 K 4 IO 2 0

90 IL.

0 2.5 ft (.76m) DEPTH> 30 o0 ILJ K 15 ft (4.6 m) DEPTH 28 D

K 80 26 ILj MONITOR N0.7 CL (OVERBANK) 24 ILI ILj I- 22 I-j 70 90 IL 2i5 ft (.76m) DEPTH+

30 0 v o0 ILj l5 ft (4.6 m) DEPTH K 28 I- 80 26 MONITOR NO. 14 (CHANNEL) 24 ILj ILj I- 22 ILI I-70 0600 I 200 I BOO 2400 TIME, hrs Figure26: River Flow and Temperature vs Time July l9, l977

50 SURVEY PERIOD l2 LLJ IO I-K 30 UNIT 3 O

O

~O LLI 0

Z 20 CL UNIT 2 O 5)

IO UNIT I 0

0600 1200 1800 2400 TIME, hrs Figure 27: Condenser Cooling Water Flow For July l9, l977

I N TAKE PUMP S FOR UNITS

///// g ///////

OVERBANK MILE SEEDING ZONE 294 DYE MONITORING STATION DIFFUSER MASON ISLAND LIGHT 294.9 TENNESSEE RIVER WHEELER RESERVOIR SCALE 0 500 IOOO ft MILE +'95 0 100 200 300m Figure 28:Seeding Zone, Monitoring Stations And Observed Behavior of Dye Cloud July l9, l977

LEGEND:

0 = 2 ft (0.6 m) DEPTH El = 6 ft( I.8m) DEPTH

~ = 8 ft (2.4m ) DEPTH b, = I2ft(3.7m) DEPTH zO I- 20 K

o~. IO LLJ TIME, hrs STATION B Kl CL Q.

z0 t- 20 K

LLJ oz O

o IO IJJ a

0800 ,0900 IOOO I IOO 1200 TIME, hrs STATION A STATION C Figure 29:Dye Concentration Outside of SkimtTIer Nail July l9, l977

30 44 CO LEGEND:

Q. 8 = 2 ft (0.6m)DEPTH Q.

8 =l2 ft(3.7m) DEPTH z'2o 4=20 ft(6. Im ) DEPTH I-I- / ~

ILL /L ~

O Ip Cd ~ ~

I LLI 0 I

g ~

O TIME, hrs STATION D f

Q.

2O O

I-I- Ip z

0 ky O

ILI 0" p TIME, hrs STATION E 03 Q

Q 20 O

I-Q zI-LLI Ip CJ zO O

Ul ~ ~

0-a 0 0800 '900 lppo I I 00 I 200 TIME, hrs STATION F Figure30: Dye Concentration in Intake Channel July l9, l977

70 45 60 50 l4 SURVEY PERIOD l2 40 O IO tt 0 4~

>0 ILj 30 8 K COMPUTED FLOW) 00 20 'TENN. RIVER MILE 293.5 IO 2

0 90 IL 0 2.5 ft (.76m) DEPTH~~ ~ ~ 30 ILj 0 ft (4.6m) 28 m I- 15 DEPTH 80 ILj 26 I CL MONITOR N0.7 (OVERBANK)

LLj 24 I-22 g 70 90 2.5 ft ( 76'm) DEPTH~

0 IL 30 O

0 ILI l5ft(4.6m) DEPTH 28 ILj K

I- 80 26 I-O LLI MONITOR NO, I4 'K

., (CHANNEL ) 24 ILj X

ILl I- X 22 ILI I-70 0600 I 200 I BOO 2400 TIME, hrs Figure 3l: River Flow and Temperature vs Time July 20, l977

4,6 50 PERIOD'2 SURVEY 40 LLI 10 I-K UNIT 3 50 CO IL Wo MO I-Z 20 UNIT 2 CL O IL.

6)

IO UNIT I 0

0600 I 200 I800 2400 TIME, hrs Figure 32: Condenser Cooling Water Flow For July 20, l977

47 TABLE 1

SUMMARY

OF TEST CONDITIONS AND RESULTS FOR BROWNS FERRY NUCLEAR PLANT INTAKE STUDIES Test Test Condition

'iverFlow Temperature From. Monitor***

Percentage in of Flow Intake from Date s~g cfs **9 cfs 4 0 h k May 18 4410 38,000 75.6 73.6 56 June 7 3420 35,000 ,77.8 77.0 63 July 19 3420 11,000 85.3 85.7, 55 July 20 3550 21,000 84.0 85.4 53

• Intake flow.

• • Average river flow at Tennessee River Mile 293.5 during test period.

• ~~Temperature recorded 'at depth of 5 feet at 1000 hrs ~

48 channel spread over the cooler overbank water which plunged un'(ier-L neath. Figure 33 shows the qualitative description of the water sur.fac(

()n July ?0. hlthou(lh som(. ol l.ii(. (iy(.(l w(rl(.r was ()t)s(.r'v(,(l (i()wrurl,r (<)rr) of the intake, it seems likely that, the source of that water was from the overbank near the edge of the channel.

I For this survey, the overbank dye concentration was approxi-

~

mately 10 ppb and the maximum cross-sectional average of the intake channel was 5.3 ppb, which implies, that 53 percent of the intake flow came from the overbank.

P C

'I t

INTAKE PUMPS FOR UNITS

////'VERBANK MILE SEEDING ZONE 294 EDDY DYE MONITORING STATION MASON ISLAND LIGHT 294.9 DIFFUSER TENNESSEE RIVER SCALE WHEELER RESERVOIR 500 IOOO ft MILE+295 0 IOO 200 300iYI Figure33:Seeding Zone, Monitoring Stations And Observed Behavior of Dye Cloud July 20, l977

50 CONCI USIONS A relatively wide overbank area is situated immediately upslreanl of the intake of the BFNP. The quantity of flow along this overbank varies w'ith reservoir stage and flow. Prior to spring filling of the reservoir, the shallow depths will prohibjt much flow over the over-bank, but after the reservoir has been raised to near the maximum level, usually in April, the depths of the overbank will permit more flow. A velocity survey conducted in May 1977 during a river flow of 38,000 ft /sec (1075 m /sec) revealed that about 3000 ft3 /sec (85 m /sec) was flowing over the overbank.

Most of the flow over the overbank is being drawn into the BFNP intake when the plant is operating in Open or Helper Modes of condenser cooling. During Open Mode, the design intake flow rate for all three units in operation is 4410 ft /sec (125 m /sec), and for Helper Mode, design flow rate is 3675 ft3 /sec (104 m /sec). These flow rates are proportionally decreased when units are not in service.

In the spring, when the reservoir is gradually warming, the large surface areas and shallow depths of the overbanks provide lil.LI>>

thermal inertia; hence, the overbank areas are generally warmer I.han the main channel. Under these conditions, buoyancy of the warmer overbank water is sometimes sufficient to prevent water in the upper three feet (one meter) from being entrained into the plant intake. This was demonstrated with a velocity survey and'a dye study. However, studies conducted during the summer which also included "a trajectory analysis using drogues showed that this phenomenon was nominal.

51 Four field surveys using Quorescent dye were performed to determine the percentage of BFNP intake flow which originated from the overbank. These tests, which were conducted during near maximum surface elevations for a wide range of typical reservoir flow and plant operational conditions, revealed that between 53 and 63 percent of the BFNP intake flow comes from the overbank when the plant is operal.ing three units in Open or Helper Modes.